1. Field of the Invention
The present invention relates to a light-emitting device and a method of manufacturing the same, and more particularly, it relates to a light-emitting device comprising a semiconductor element layer and a method of manufacturing the same.
2. Description of the Background Art
A light-emitting device such as a light-emitting diode device employing a nitride-based semiconductor is actively developed at present. In order to apply a light-emitting diode device employing a nitride-based semiconductor to a light source for a lighting apparatus, improvement of the light output characteristic of the device and increase of an applied current have recently been developed in particular. In order to form such a light-emitting diode device employing a nitride-based semiconductor, a semiconductor element layer is grown on a sapphire substrate requiring a lower cost than a high-priced substrate of GaN.
Further, a light-emitting diode device emitting light created in a semiconductor element layer (emission layer) from the side of a sapphire substrate employed as a growth substrate for growing the semiconductor element layer is known in general. In addition, a technique of improving light extraction efficiency in the aforementioned light-emitting diode device emitting light from the side of the sapphire substrate by inclining the side surfaces of the device by a prescribed angle is also known in general, as disclosed in Japanese Patent Laying-Open No. 6-244458 (1994) or 10-341035 (1995), for example.
The aforementioned Japanese Patent Laying-Open No. 6-244458 or 10-341035 discloses a light-emitting diode device formed by growing a semiconductor element layer on a translucent substrate such as a sapphire substrate so that a light emission surface (surface of the translucent substrate) and the side surfaces of the translucent substrate and the semiconductor element layer form an acute angle. According to the aforementioned Japanese Patent Laying-Open No. 6-244458 or 10-341035, light totally reflected on the light emission surface is incident upon the side surfaces inclined by a prescribed angle with respect to the light emission surface, whereby the path of the light can be so changed that the angle of incidence of the light with respect to the light emission surface is smaller than the critical angle. Thus, the light totally reflected on the light emission surface can also be emitted, whereby the light extraction efficiency can be improved.
According to the aforementioned Japanese Patent Laying-Open No. 6-244458 or 10-341035, however, the light emitted from the side of the transparent substrate passes through the interface between the transparent substrate and the semiconductor element layer. In this case, the light is disadvantageously reflected on the interface between the transparent substrate and the semiconductor element layer due to different refractive indices of the transparent substrate and the semiconductor element layer. Therefore, the quantity of light emitted from the light emission surface (surface of the translucent substrate) is disadvantageously reduced despite the side surfaces of the device inclined for improving the light extraction efficiency. Consequently, it is problematically difficult to improve the light extraction efficiency.